https://bugs.freedesktop.org/show_bug.cgi?id=99275
--- Comment #27 from Michel Dänzer michel@daenzer.net --- (In reply to Reimar Imhof from comment #26)
Together with comment #24 there is a render bug in kernel 4.8 that shows up at 100% cpu load. With kernel 4.9 this same bug shows up at 0% / idle cpu load.
With af79ad2b1f337a00aa150b993635b10bc68dc842 Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip it changed from "bug shows at 100% load" to "bug shows at 0% load". And the change is something about the scheduler. To me this seems likely.
Not really. That commit is a pure merge commit, which makes it unlikely that it behaves any differently from either of its parent commits. So git bisect should have identified one of its ancestor commits instead. The fact that it identified a pure merge commit indicates that the result is incorrect, most likely because at least one commit along the way was incorrectly classified as good (or bad).